LG 50PQ300 spark from Y-Sus

[viduka]

Anyone help with a problem with a LG 50PQ3000.
Problem is there is a spark from the Y-Sus board. Visible flash the run along the metal back panel just under the Board.
TV works fine. I've remove the board and cleaned it and this seemed to cure it but it came back the following morning.

[tom66]

Re: LG 50PQ300 spark from Y-Sus

Could be flash-over - there is about 400V on some parts of the Y-sus, and maybe twice that around the flyback converter. Check for carbonisation, dust build up and missing insulation pads.

[freakaftr8]

Re: LG 50PQ300 spark from Y-Sus

Some TVs come with insulator material to prevent this especially in high current tracks of a circuit board. Sometimes the insulator was removed upon a repair and not replaced and other times poor design characteristics are the cause. Also look for cold solder joints on the board where the spark is.

[viduka]

Re: LG 50PQ300 spark from Y-Sus

Ok. I've made a mistake somewhere. Removed the board. Cleaned again with compressed air. Removed the insulating pads turned them and refitted.
Refitted the board and my small spark became a much larger spark and a nice bang.
TV now displays no picture.
Upon checking the board I know see scorch mark on main Cap bank which matches scorch mark on the metal panel of TV.
Question is should I bother replacing the CAP or is the board / Buffers likely to be goosed ?
I've attached Pictures of Scorch marks on panel and Board. Picture of Cap bank and Pic of full board.
Any help would be great.

[tom66]

Re: LG 50PQ300 spark from Y-Sus

No insulating pads, that's your problem!!
You are probably lucky, I would guess Y-sus fuse is popped but replacing that will fix the issue.
But for some reason all the insulating rubber pads are missing, where have they gone??

[viduka]

Re: LG 50PQ300 spark from Y-Sus

No the pads are there. All I did was remove them turn them 180 and reapply.

[tom66]

Re: LG 50PQ300 spark from Y-Sus

So how did you get a spark with the pads in place? I can see one, but there should be many more.

[viduka]

Re: LG 50PQ300 spark from Y-Sus

That I don't know. TV has never been open since new. As per Pics 3 pads are in place but Scorch Mark is on Cap bank which had no pad.

[tom66]

Re: LG 50PQ300 spark from Y-Sus

I fixed a 42" PQ3000 recently, it had pads on the cap bank. I know it's a different panel 42" vs 50" but you'd expect it to be similar. I would advise you find some insulating material and install it. Then replace the fuse. Luckily, I think the worst that could have happened is a blown fuse. Possibly the technician at the factory forgot to install it, or was too lazy that day.

[Ahakim]

Re: LG 50PQ300 spark from Y-Sus

There must be insulating pads in such TVs. High current/voltage could cause such sparks from too close components from back or to each other...
Check for carbonisation in spark area...

[Alastair E]

Re: LG 50PQ300 spark from Y-Sus

Well--That last pic looks like a classic dry-joint to me....
--Solder it up, check for any shorts, away to go.....

The mounting-lugs of the boards should keep 'em clear of the metalwork anyway, by around half a cemtimetre....

[R_J]

Re: LG 50PQ300 spark from Y-Sus

Like Alastair said, looks like a poor solder connection on the caps that has been arcing, If the voltage was so high as to arc to the panel it would be arcing between the capacitor connections first as they are a lot closer together. The black on the panel is just a result of the arc not where it arced to.
I would inspect the whole board for poor solder connections, especially on the other caps, if the board is still good.